The present invention relates to a radio communication apparatus, which performs radio communications using a plurality of antennas, and a transmission power controlling method.
A conventional radio communication apparatus will be explained with reference to FIG. 1.
FIG. 1 is a block diagram showing an entire configuration of the conventional radio communication apparatus. In the radio communication apparatus shown in FIG. 1, a reception RF circuit 3 amplifies signals, which are received by an antenna 1 and input through a coupler 2, and frequency-converts the amplified signals to intermediate frequencies or baseband frequencies.
An SINR measurement circuit 4 measures a ratio (Radio) of a sum of interference wave reception power (Interference) and noise power (Noise) to desired wave reception power (Signal). Comparison between this SINR and a target SINR is performed. If this SINR is smaller than the target SINR, the SINR measurement circuit 4 outputs Transmission Power Control information (hereinafter referred to as xe2x80x9cTPCxe2x80x9d) to control a communication counterpart to increase transmission power. While, if this SINR is larger than the target SINR, the SINR measurement circuit 4 outputs TPC to control the communication counterpart to reduce transmission power.
A demodulating circuit 5 demodulates received signals, and separates received data and TPC from each other.
A multiplexing circuit 6 multiplexes a TPC output from the SINR measuring circuit 4 and transmitted signals. As a multiplexing method, for example, there is a method in which TPC and transmitted signals are assigned to slots.
A modulating circuit 7 modulates an output signal of the multiplexing circuit 6. A transmission RF circuit 8 frequency-converts an output signal of the modulating circuit 7 to a radio frequency, and amplifies it based on TPC, and transmits it through the coupler 2 and antenna 1.
As mentioned above, the conventional radio communication apparatus provides instructions to the communication counterpart such that SINR as one index of reception quality becomes constant, thereby maintaining the reception quality constant.
In accordance with a recent sharp increase in subscribers, there has been demanded a radio communication system in which communication quality and an increase in the number of containable users are improved. In response to this demand, there is a system in which directivity is sequentially changed in accordance with the positions of communication counterparts or a propagation environment.
In this system, a directional gain, which means a gain of s radiation pattern respect to a direction of a subscriber, sometimes change from moment to moment. For this reason, if only transmission power is singly controlled, similar to the conventional radio communication apparatus having the constant transmission directivity, an error in reception power between the communication counterpart and the radio communication apparatus increases, and this prevents the attainment of the purpose of improving the increase in the number of containable users.
In other words, if the directional gains are increased, signals can be transmitted to the communication counterpart by use of power more than necessary, and the communication counterpart can receive the signals with sufficient power, but this causes interference with respect to the other communication apparatuses, and results in deterioration of reception quality. While, if the directional gains are decreased, the communication counterpart can not receive the transmitted signals with sufficient power, resulting in deterioration of reception quality.
An object of the present invention is to provide a radio communication apparatus, which can control transmission power such that reception power of a communication counterpart becomes constant and which can improve communication quality and an increase in the number of containable users in a system wherein directivity is sequentially changed in accordance with the positions of communication counterparts or a propagation environment, and provide a transmission power control method.
The above object can be attained by calculating a correction value of transmission weight based on directional gains, controlling a gain of transmission power amplifier based on the correction value and transmission power control information, and calculating the transmission weight based on reception weight and correction values of the directional gains calculated from the reception weight.